A METHOD FOR EXPLICIT MODELING OF BARRIER FAILURES IN MULTI-COMPARTMENT FIRE SCENARIOS

摘要

A fire PRA plant response model is to be capable of identifying significant contributors to CDF and LERF, including plant initiating events, accident sequences, and equipment unavailabilities. Multi-compartment fire scenarios consist of afire initiating event and fire damage occurring in one physical analysis unit, followed by propagation of effects from the fire to one or more additional physical analysis units (PA Us) due to barrier failure or unavailability. Based on peer review observations, multi-compartment fire scenario modeling quantifies the likelihood for multi-compartment impacts typically in side calculations, and the contributions from barrier unavailabilities are not explicitly captured as a result. This approach can still meet Capability Category II of the ASME / ANS PRA Standard, if the scenarios in the base model are not risk-significant. This is typically difficult to know in advance, and rework is needed later if any multi-compartment scenario is risk-significant. Furthermore, any PRA applications would need to revisit the risk-significance of multi-compartment scenarios, particularly applications that involve fire barriers. An effective alternative is presented that performs cutset post-processing that explicitly models the exposing compartment scenarios and barrier unavailabilities for all unscreened multi-compartment scenarios and typically requires no additional analysis resources.